With respect to pharmaceutical compounds which have an asymmetric center, it is known that optical isomers of some of such compounds respectively have different physiological activities. That is, often only one of the isomers has physiological effect in vivo or only one of them has terato-geneticity as seen in thalidomide. However, it is difficult to optically separate a racemic compound by a conventional method such as distillation, crystallization, etc. Thus most of the pharmaceutical compounds having an asymmetric center are marketed in the form of a racemic compound.
Under the circumstances, a commercial process, by which only an optical isomer of various such pharmaceutical compounds and intermediate compounds therefor can be isolated, is strongly desired. Because, if only physiologically active and useful isomers can be used as therapeutics, a small dose suffices and abatement of undesirable side effect is expected.
Although physiologically active isomers of mevalonolactone compounds are very useful for prevention and treatment of hyperlipemia, arteriosclerosis, etc., there has been no commercial process for optical resolution.
The object of this invention is to solve the above-described problem. In other words, the object of this invention is to isolate optically active isomers of mevalonolactone compounds with high purity in a commercial scale.